104 SECULAR INCREASE IN SIZE CHAP, iv have left a dwarfish offspring; that there were giants of old, and that there is a puny race to-day. As a matter of ffxct, the study of the gradual evolution of the early Tertiary Mammalia Into their descendants of later times shows very plainly the truth of this interesting generalisation: That the primitive types were all small creatures, and that in those instances where we can trace a pedigree, there was a gradual increase in size up to a point where greater increase led to extinction. We point out later on a number of facts illus- trating this matter in detail. It has been ascertained, for instance, that the pedigree of the Horses, the Camels, the Ehino- ceroses, and many other groups, commences with small forms and culminates in large ones. It may be urged that such animals as the Tapir are to-day smallish forms, and that related to them in the past were the gigantic Titanotheres; but in this and similar cases it will be found that the extinct giants were not in the direct line of pedigree, but represented side-branches which waxed huge on their own account and then disappeared.